Sheet 6 Flashcards
Is Tay Sachs disease dominant or recessive?
Recessive
What causes Tay Sachs disease?
The enzyme Hexosaminidase-A that metabolizes lipids is
defective = lipid accumulation and build up = cell damage and death
Tay Sachs disease is an example of:
A Classical lysosomal storage disorder
Which gene encodes for Hexosaminidase-A?
HEXA gene on q arm of chromosome 15
15q – region 14
When do clinical features start to show in Tay Sachs disease?
In the first months of
life
When do Tay Sachs patients die?
Within the age of 3-4 yrs
What are the clinical features of Tay Sachs disease?
1) Neuromotor difficulties
2) Psychomotor impairment
3) Seizures
4) Tremors
5) Other classical features of CNS damage
In homozygous mutant individuals of Tay Sachs, the enzyme is:
Defective; the metabolic
activity of the enzyme is ZERO.
In homozygous normal individuals of Tay Sachs, the metabolic activity of the enzyme is:
100%
In heterozygous mutant individuals of Tay Sachs, the enzyme is:
Neither fully active nor inactive (incomplete dominance); metabolic activity is between 0-100%
At the biochemical level, Tay Sachs disease is:
Incomplete dominant
At the genetic/molecular level, Tay Sachs disease is:
Codominant
Sickle cell anemia:
a) Phenotypically:
b) Biochemically:
c) Genetically/Molecularly:
a) Complete dominance
b) Incomplete dominance
c) Codominant
Tay Sachs disease:
a) Organismal:
b) Biochemically:
c) Genetically/Molecularly:
a) Recessive
b) Incomplete dominance
c) Codominant
What is an example of multiple alleles?
Blood groups
What is pleiotropy?
1 gene defect causes multiple phenotypic effects
Is Cystic Fibrosis dominant or recessive?
Recessive
What is the Cystic Fibrosis gene?
CFTR
What is an example of pleiotropy?
Cystic Fibrosis
What are the phenotypic effects of Cystic Fibrosis?
1) Infection of air sinuses (sinusitis).
2) Mucous Build up and bacterial infection in the lungs.
3) Salty Sweating (more NaCl in sweat)
4) Biliary duct will be filled with mucous = blocked.
5) Pancreatic duct will also be blocked thus rendering the pancreatic function.
6) Intestines filled with mucous = the GI is incapable of absorbing food.
7) Complications in Males and Females reproductive organs
Which is the easiest and typical test to start with to detect cystic fibrosis?
Salty Sweating
What is Epistasis?
A gene at one locus alters the phenotypic expression
of a gene on another locus.
Tay Sachs disease and Cystic Fibrosis are:
Single gene disorders
Quantitative variations usually indicate which type of inheritance?
Polygenic inheritance, an additive effect of two or more genes on a single phenotype.
